In recent years, local area network (LAN) applications have become more and more prevalent as a means for providing communications between personal computers, work stations and servers. Because of the breadth of its installed base, the 10BASE-T implementation of Ethernet remains the most pervasive, if not the dominant, network technology for LANs. However, as the need to exchange information becomes more and more imperative, and as the scope and file size of the information being exchanged increases, higher and higher communication speeds (i.e., greater bandwidth) are required from network interconnect technologies. Among the high-speed LAN technologies currently available, fast Ethernet, commonly termed 100BASE-T, has emerged as the clear technological choice. Fast Ethernet technology provides a smooth, non-disruptive evolution from the 10 megabit per second (Mbps) performance of 10BASE-T applications to the 100 Mbps performance of 100BASE-T. The growing use of 100BASE-T interconnections between servers and desktop personal computers is creating a definite need for an even higher speed network technology at the backbone and server level.
In an attempt to address the need for faster data communications, various groups have developed standards that specify high speed data transfers between components of data communication systems. For example IEEE standards 802.3ab and 802.3z define Ethernet systems for transferring data at rates up to one gigabit per second (1 Gbit/s). IEEE standard 802.3ae defines an Ethernet system for transferring data at rates up to 10 Gbits/s. These standards are now utilized in Gigabit Ethernet or 1000Base-T interconnections.
With the advent of Gigabit Ethernet or 1000Base-T interconnections, Gigabit Interface Converters (GIGABIT INTERFACE CONVERTER) are becoming increasingly popular for providing 1000BASE-T connectivity. GIGABIT INTERFACE CONVERTERs conform to well-defined specifications and operate by the standards set by the above-mentioned IEEE standards, as well as non-IEEE standards, such as Gigabit Media Independent Interface (GMII) or Extended Gigabit Media Independent Interface (EGMII). Also, GIGABIT INTERFACE CONVERTERs have become readily available as off-the-shelf components that make the design and implementation of a Gigabit Ethernet network or backbone relatively simple and economical.
The GIGABIT INTERFACE CONVERTER specification was developed by a group of electronics manufactures in order to arrive at a standard small form factor transceiver module for use with a wide variety of serial transmission media and connectors. The specification defines the electronic, electrical, and physical interface of a removable serial transceiver module designed to operate at Gigabit speeds. A GIGABIT INTERFACE CONVERTER provides a small form factor pluggable module which may be inserted and removed from a host or switch chassis without powering off the receiving socket. The GIGABIT INTERFACE CONVERTER standard allows a single standard interface to be changed from a first serial medium to an alternate serial medium by simply removing a first GIGABIT INTERFACE CONVERTER module and plugging in a second GIGABIT INTERFACE CONVERTER module having the desired alternate media interface.
The GIGABIT INTERFACE CONVERTER standard can provide communications over copper wire or optical fibers. GIGABIT INTERFACE CONVERTER allows network managers to configure each gigabit port on a port-by-port basis for short-wave (SX), long-wave (LX), long-haul (LH), and copper (CX) physical interfaces. LH GIGABIT INTERFACE CONVERTERs extend the single-mode fiber distance from the standard 5 km to 10 km. In addition to single-mode fiber, multi-mode fiber is also utilized as a medium for optical data transmission in a 1000Base-T network.
As schematically illustrated in FIG. 1, in a full-duplex 1000Base-T configuration 1 using GIGABIT INTERFACE CONVERTERs 2 and 3, two separate optical fibers 4 and 5 are needed to achieve simultaneous data transmission in two directions between two stations on a point-to-point link. A first optical fiber 5 carries optical signals from node A to node B in a first direction, and a second optical fiber 4 carries optical signals from node B to node A in a second direction, opposite to the first direction. Such a configuration is schematically illustrated in FIG. 1. In another configuration, an optical communication pipe, not shown, is created by bundling a plurality of optical fiber pairs. A plurality of GIGABIT INTERFACE CONVERTER transceivers can be trunked together with multiple pairs of optical fiber to create a high band-width pipe. Such a configuration may be of an array 2-channel, 4-channel, or 8-channel of GIGABIT INTERFACE CONVERTER transceivers trunked together.
At the present time, a Hewlett Packard™ GIGABIT INTERFACE CONVERTER with 1.25 Gbps transmission speed can be purchased for about $126, and a 3COM™ 1000BASE-LX GIGABIT INTERFACE CONVERTER can be purchased for $1,020.00. As for the optical transmission medium, the connection of various nodes in a network are usually owned by communications companies such as Sprint™, AT&T™, and the like. Since it is prohibitively expensive to create a fiber optic network infrastructure from the ground up, most companies needing fiber optic connections for their network find it most practical to lease fiber optic lines.
Leasing costs are generally based on the number of fibers needed and the distance through which optical data are to be transmitted. For example, a 15-mile single-fiber connection lease may cost about $1 million for 5 years in the United States. As noted above, existing standards and technology require that GIGABIT INTERFACE CONVERTER ethernet connectivity use a minimum of two fibers for full-duplex optical communication. Thus, at least two optical fibers must be leased for a minimum configuration of Gigabit Ethernet using GIGABIT INTERFACE CONVERTERs.
When Asynchronous Transfer Mode (ATM) or cell relay communication is commonly used as the backbone or core of communications networks, it is known to utilize methods and apparatus for full-duplex bi-directional long-haul communication using a single optical fiber using Wave Division Multiplexing (WDM) and laser-based transceivers.
As an example, U.S. Pat. No. 5,452,124 to Baker discloses a four-port WDM filter and a single erbium-doped optical amplifier to implement a dual wavelength bi-directional single fiber optical amplifier module. Baker discusses conventional two-fiber transmission and its drawback, and introduces WDM technology and a single-fiber bi-directional communication system. The focus of Baker is, however, an optical line amplifier module for the single-fiber bi-directional communication system.
In another example, U.S. Pat. No. 6,211,978 to Wojtunik discloses a multichannel wave division multiplex system for simultaneous bi-direction transmission through a single optical fiber. Wojtunik teaches modulated light signals having the same wavelength traveling in opposite directions over a single fiber at the same time. In yet another example, U.S. Pat. No. 5,633,741 to Giles discloses multichannel optical fiber communications having bi-directional transmission with at least two WDM channels in opposite transmission directions in a single fiber. More WDM communication systems are disclosed in U.S. Pat. No. 5,909,294 to Doerr et al., U.S. Pat. No. 6,130,775 to Yang, U.S. 2001/0038478A1 and 2001/0038477A1 to Hwang, and Liaw et al.'s “Multichannel Bidirectional Transmission using a WDM/MUX/DMUX pair and Unidirectional In-Line Amplifiers” IEEE Photonics Technology Letters, Vol. 9, No. 12, December 1997.
These WDM communication systems, although varied in their design, are generally found in ATM communication systems, and require an extraordinarily high-cost investment in customized hardware and software. The cost for designing and implementing a WDM communication system, without the optical fiber, can be about a quarter of a million to several millions of dollars. Accordingly, single fiber bi-direction optical signal transmission currently is very expensive.